import { mapGetters } from 'vuex'
const version = require('element-ui/package.json').version // element-ui version from node_modules
const ORIGINAL_THEME = '#ED5555' // default color
export default function () {
    return {
        data() {
            return {
                themeVal: ORIGINAL_THEME
            }
        },
        created() {
            this.themeVal = this.theme
        },
        watch: {
            themeVal(val, oldVal) {
                this.$store.commit('SET_THEME', val)
                this.updateTheme(val, oldVal)
            }
        },
        computed: {
            ...mapGetters(['theme'])
        },
        methods: {
            updateTheme(val, oldVal) {
                if (typeof val !== 'string') return
                const head = document.getElementsByTagName('head')[0]
                const themeCluster = this.getThemeCluster(val.replace('#', ''))
                const originalCluster = this.getThemeCluster(oldVal.replace('#', ''))
                const getHandler = (variable, id) => {
                    return () => {
                        const originalCluster = this.getThemeCluster(
                            ORIGINAL_THEME.replace('#', '')
                        )
                        const newStyle = this.updateStyle(
                            this[variable],
                            originalCluster,
                            themeCluster
                        )

                        let styleTag = document.getElementById(id)
                        if (!styleTag) {
                            styleTag = document.createElement('style')
                            styleTag.setAttribute('id', id)
                            head.appendChild(styleTag)
                        }
                        styleTag.innerText = newStyle
                    }
                }

                const chalkHandler = getHandler('chalk', 'chalk-style')

                if (!this.chalk) {
                    const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`
                    this.getCSSString(url, chalkHandler, 'chalk')
                } else {
                    chalkHandler()
                }

                const link = [].slice.call(
                    document.getElementsByTagName('head')[0].getElementsByTagName('link')
                )
                for (let i = 0; i < link.length; i++) {
                    const style = link[i]
                    if (style.href.includes('css')) {
                        this.getCSSString(style.href, innerText => {
                            const originalCluster = this.getThemeCluster(
                                ORIGINAL_THEME.replace('#', '')
                            )
                            const newStyle = this.updateStyle(
                                innerText,
                                originalCluster,
                                themeCluster
                            )
                            let styleTag = document.getElementById(i)
                            if (!styleTag) {
                                styleTag = document.createElement('style')
                                styleTag.id = i
                                styleTag.innerText = newStyle
                                head.appendChild(styleTag)
                            }
                        })
                    }
                }

                const styles = [].slice.call(document.querySelectorAll('style'))

                styles.forEach(style => {
                    const {
                        innerText
                    } = style
                    if (typeof innerText !== 'string') return
                    style.innerText = this.updateStyle(
                        innerText,
                        originalCluster,
                        themeCluster
                    )
                })
            },
            updateStyle(style, oldCluster, newCluster) {
                let newStyle = style
                oldCluster.forEach((color, index) => {
                    newStyle = newStyle.replace(new RegExp(color, 'ig'), newCluster[index])
                })
                return newStyle
            },

            getCSSString(url, callback, variable) {
                const xhr = new XMLHttpRequest()
                xhr.onreadystatechange = () => {
                    if (xhr.readyState === 4 && xhr.status === 200) {
                        if (variable) {
                            this[variable] = xhr.responseText.replace(/@font-face{[^}]+}/, '')
                        }
                        callback(xhr.responseText)
                    }
                }
                xhr.open('GET', url)
                xhr.send()
            },

            getThemeCluster(theme) {
                const tintColor = (color, tint) => {
                    let red = parseInt(color.slice(0, 2), 16)
                    let green = parseInt(color.slice(2, 4), 16)
                    let blue = parseInt(color.slice(4, 6), 16)

                    if (tint === 0) {
                        // when primary color is in its rgb space
                        return [red, green, blue].join(',')
                    } else {
                        red += Math.round(tint * (255 - red))
                        green += Math.round(tint * (255 - green))
                        blue += Math.round(tint * (255 - blue))

                        red = red.toString(16)
                        green = green.toString(16)
                        blue = blue.toString(16)

                        return `#${red}${green}${blue}`
                    }
                }

                const shadeColor = (color, shade) => {
                    let red = parseInt(color.slice(0, 2), 16)
                    let green = parseInt(color.slice(2, 4), 16)
                    let blue = parseInt(color.slice(4, 6), 16)

                    red = Math.round((1 - shade) * red)
                    green = Math.round((1 - shade) * green)
                    blue = Math.round((1 - shade) * blue)

                    red = red.toString(16)
                    green = green.toString(16)
                    blue = blue.toString(16)

                    return `#${red}${green}${blue}`
                }

                const clusters = [theme]
                for (let i = 0; i <= 9; i++) {
                    clusters.push(tintColor(theme, Number((i / 10).toFixed(2))))
                }
                clusters.push(shadeColor(theme, 0.1))
                return clusters
            }
        }
    }
}
